Band antenna



P. P. GAME-:T

BAND ANTENNA v Feb. 13, 1945.

Filed March 27, 1942 Patented Feb. 13, 1945 BAND ANTENNA Pierre PaulGarnet, Paris, France; vested in the Alien Property CustodianApplication Marchl 27, 1942, Serial No. 436,535

A In France March 28, 1941 i Claims.

The present invention relates to improvements in multiple strandaerials, and aerials comprising a shaped nat conducting band,particularly for very high frequencies.

The invention relates more particularly to aerials or aerial systemshaving a high emciency and makes it necessary to modify thematchingcircuits when working `with a number of differentr wavelengths.I

On the other hand, aerials are generally'located at inaccessible placesfor'instance on the top of amast or of `a building and, in any case, oneencounters great diiculties in changing the aerial structure or thetransmission line once they are set up. However, it is most desirable tobe able to use such a unit inV a 'predetermined range of wave lengths,the aerial retaining inthe said range the same properties of radiationandthe same characteristic features from the point of view ofthetransmission orreceiving apparatus withwhich it is coupled.

The present invention offers this latter advantage without making itnecessary, in any way, tomodify the mechanical and electricalcharacteristlcs of the aerial and of the matching circuit once they areset up and mounted, the said.

aerial being designed so as to obtain` a large aperiodicity, the outputradiated by this aerial remaining constant over a large range of Awavelengths, and itsoptimum operation being such that'it does not require anenergizing circuit specially designed to have the best conditions ofcoupling and of matching of impedance.

My improved aerial permitting to attain the above mentioned objectspresents the characteristic features which will appear'frorn thefollowing description and more 'particularly from the appended claims.e.

Aerials according to the invention are shown by wayof examples in theaccompanying drawing, in which:

, Figure 1 is a general perspective view of the aerial from the iront.

Figure 2 is atop plan view of the aerial.

(Cl. Z50-33) Figure 3 shows a detail of the top terminal loo Flzigllre 4shows the developed surface -of the terminal loop on a plane.

Figure 5 is a diagram of the elementary aerial element of which thecomplete aerial may be considered to be composed.

The aerial is formed of a iiat conducting band I, a secondiiat'conducting band 2 parallel to band I, and a flat conducting band 3parallel to band 2 and in line with band I;' these bands vi and 3, onthe one hand, and 2, on the other hand, are spaced from each other by ladistance which .is small with respect to the radiated or received wavelength.

The extremities 4 of band` `I,' and 5 of band 3, are bent for instanceata right angle at 6 and l, and carry terminals 8 and 9 for securingboth wires of the transmission line or the connection wires of thecoupling means.

The bands I and 2, on the one hand, and 3 and 2, on the other hand, areconnected together at their ends by a terminal band I0 and by a terminalband I I respectively, which are bent in the form of a loop which issuch that when developed orr spread out on a plane it forms a parabolicsurface. n

The electrical constants of the aerial depend upon the followingdimensions: The tip-to-tip distancerat the rear of the structure shownin Fig. 1, L1 the length ofthe -branch 2, and of the lbranch Iv togetherwtih the branch 3, measured respectively onl the rear edges I2, and I3-I4. e

L2 the length of the branch 2, and also of branch l together with branch'3, measured on the front edges I5, I6 and I1.

O1 the thickness distance at the rear from left to right between theedges I3 and I4, on the one hand, and I2, on the other hand, of thebranches I, 3 and 2.y O2 the thickness distance-at the front from lefttoriglit between the edges I6 or I1, on the one hand, and I5, on theother hand, of the branches I, 3 and 2. b the depth of the aerial fromfront to back. f The dimensions L1, L2, O2 and b can vary over aconsiderable range according to the desired range of aperiodicity andthe scale of frequencies to be transmitted or received. From this fact,the Vgeneral form of the aerial can be considerably modled according tothe choice of the preceding dimensions.

An aerial of the described type possesses acomparatively low imepdance;it is necessary to en- ,on the other hand.. of, rectilinear form,lparallel and separated front another by a distance which is small withrespect to the radiated or received wave length. These strands areconnected at their extremities by terminal loops 2| and 22.

The length of each of these elementary aerialsvaries progressivelywithin the limits L1, L2; the,` distance between each of the strands1.9. and 2.5', on the one hand, and I8, on the other hand, variesprogressively between O1 and O2. Thus, the cornplete structure istapered in both length and breadth in a direction perpendicular to theseelementary aerials, and has substantially the shape of the frustum of acone.`

Suppose two points 23, 24 of the wires ofthe elementary aerial at thesame height X over the lower tip point 25. 'Elie-vakliteoftheL currentsIl and Iai as a function of time is given to a first approximation bythefollowing expression-r 11:21 sin whe-re Alissa constant, T' theperiodof: the. oscillations, it the, wave length and. t thev time,

These equations are true with the singie assumption that the terminalloops. do not modify the propagation of the: waves, and experiencecontinus' this; fact.

One;` sees. that Yboth theseequations are identical in their form withthe single exception of the. sign. mi theterm From the; point of view ofthe: eld produced at al great distancev and. since the distancev betweenboth strands is small withrespect to the wave length, the radiation isidentical: to that of a sin-gle conductor the` intensity of which `wouldbe the sum of both preceding intensities, which sum has forli-tsexpression:

I N+ 12= 2li` sin 21E-, cos an? One sees that for standingy waves this'intensity corresponds with, that of a dipole tuned to the wave lengththe intensity `of which at the current loop is equal to twice theYintensity in each branch, This calculation .shows welrthe radiationpower of this elementary aerial and experience `confirms it' entirely.

The .aerial according to the presentA invention being, formed ofv aninfinite number of these elementary aerials,l i'tl has a radiation'valuewhich can be considered for a given frequency as the sum of the partialradiations of `each elementary aerial while taking into account theirmutual inductance.

Experience shows that the radiation resistance of' this unit is nearly'constant overa large range of wave lengthsand that, on the otherhand,its aperiodicityis obtained within wide limits even then when theenergizing circuit does not A correspend to the best conditions ofcoup-ling and ofm'atchingof the impedance.

The invention is generally applicable andcan be applied to all theaerials comprising systems of any antennae (radiogoniometers,radiobeacons); it is more particularly advantageous for transmittersworking various different stations for transmitting aerials or receivingaerials `with wide band pass characteristics, in order to obtain theminimum distortion during transmission or reception, as of the image intelevision.

Ifclaim: 1

l. A broad band antenna particularly for ultra high frequencies,comprising a conducting band having substantially the shape of thefrustum of a cone, said band being discontinuous at a region of itsconical surface for the application of operati-ng, terminals to itsportions adjoining said region. y

2; A broad band antenna particularly for ultrahigh frequencies,comprising .a conducting band having substantially the shape of thefrustum of a cone, said band being discontinuous at a region of itsconical surface for the lapplication ofv operatingA terminals to itsportions adjoining said region, the smallest dimension of the base' ofsaid cone being small with'rel'ation to the operating wave length.

31. Abroad band antenna particularly for ultra high frequencies,comprising a conducting bandl having substanti'ally'the shape of thefrustum of acone whose base is a figureV composed of two parallel linesof substantially equal length joined together at their respectiveends bycontinuous length.

4. A broad band antenna particularly for ultra-high frequencies,comprising a conducting band' having substantially the shape of thefrustumof a cone whose base is a figure composed" of two parallel linesof substantially equal length' joined togethery at their respective endsby continuous curved' lines, the distance'betwee'n said paralleldnesbeing small with relation to their' length and smallwith relation to theoperating wave length, saidy band being discontinuous at' a regionthereof for the application of operatingterminals to itsI portionsadjoining saidf'region.

5'. A broad band antenna particularly for ultra highfrequencies,comprisinga conducting band having substantially the shape of thefrustum of a cone whose base is a figure composed of two parallel linesof substantially equal length joined together at their respective endsby continuous curved lines, the distance. between saidparallel linesbeing small with relation to their length and small with relation to theoperating wave length, said band being discontinuous at a regionintermediate and substantially midway of a longside thereof for theapplication of operating ter# minals to its portions adjoining saidregion.

6. A broad band antenna particularly'for ultrahigh frequencies,comprising a conducting band shaped to form a substantiallycontinuous'clos'ed surface having a longitudinal' plane of'symmet'ryVand having a cross-section defining a plane perpendicular to said planeof symmetry and constituted of two long parallel lines of equal lengthconnected together at their ends by continuo-us curves, said surfacebeing tapered in both length and breadth perpendicular to the plane ofsaid cross'section, thedistan'ce between' said parallel lines beingsmall with relation to 'their length and small with relation to theoperating lwave length '7. A broad band antennaA particularly' forullt'rahigh frequencies,` comprising a conducting band constitutedy ofthe surface generated by translating parallel to itself a closed planefigure which is long relative to its breadth, and the dimensions of saidgure being lat the same time continuously varied progressively in thesame sense of magnitude in its successive positions as it is sotranslated, the distance between the long branches of said gure beingsmall with relation to the operating wave length.

8. A broad band antenna particularly for ultrahigh frequencies,comprising a conducting band constituted of vthe surface generated bytranslating parallel to itself a plane gure consisting of two longparallel lines whose ends are connected together by curves, and thedimensions of said gure being at the same time continuously variedprogressively in the same sense of magnitude in its successive positionsas it is so translated, the distance between said parallel lines beingsmall with relation to the operating wave length.

9. An antenna according to claim 8, the terminal curved surfacesconnectingY the long sides of said surface whose elements are parallel,being surfaces which are -parabolic surfaces when de veloped on a plane.

10. An antenna according to claim 8, one of the long sides of saidsurface being discontinuous at a region thereof intermediate its lengthfor the application of operating terminals thereto to its portionsadjoining said region.

PIERRE PAUL GAMET.

